Presently, many industrial process and operations depend on the proper and continued operation of machines and, in particular, on the proper and continued operation of rotating machines such as motors. The number of such rotating machines in operation today is significant. For example, some have estimated that approximately 70% of all of the electricity produced in this country goes to power rotating machines. Further, the proper operation of such machines can have a significant economic impact on the operation of industrial plants as the failure of a key machine, for even a short time period, can cause an entire assembly line to come to a halt. In certain industries, for example the paper mill industry, typical motor failure can result in costs in excess of $20,000 per hour when the motor is down.
In an effort to ensure reliable and continued operation of such machines, and to avoid unexpected failures, many have attempted to employ non-intrusive diagnostic or monitoring methods or systems to locally monitor such machines in an effort to determine and, ideally, predict machine failure. One goal of such systems and methods is to allow their users to identify potential problems at an early stage and either take steps to avoid the potential problem or replace the suspect machinery.
Despite the widespread interest in diagnostic systems as described above, a practical, reliable, low cost and convenient diagnostic system for machines in an industrial environment has not yet been developed. This is especially true with respect to rotating machines such as motors, where the absence of an effective, low-cost diagnostic system or method of diagnosing motor health and life prediction is noticeable.
Prior art attempts to develop effective motor diagnostic systems and methods have been limited. The vast majority of such systems simply locally monitor a specific machine according to a fixed monitoring process to determine whether it is operating within a "fault state" (i.e., a limited, predefined operating state) or a "no-fault state." These systems, while providing some slight advance warning before a machine fails, do not provide information of the type that may be readily used for preventative maintenance or for scheduled replacement of certain machines. Also, the local monitoring processes used in such systems typically are derived from laboratory tests on related machines and are, thus, not highly accurate in field situations.
In addition to the above, many known motor diagnostic systems and methods require the use of complicated, space-requiring, and expensive detectors and/or transducers for proper operation. For example, when dealing with variable speed motors, one of the key parameters often used in known systems is the rotational speed of the rotor. Often, the rotational speed is determined through the use of an encoder or other similar device which includes a rotating member coupled to the rotor of the motor and a stationary member that is coupled the stator and that interacts with the rotating member to produce an output signal representative of the rotational speed of the rotor. The components required by such encoders often require space that could otherwise be effectively used, result in increased motor costs, and are subject to failure and/or breakage. Accordingly, many known diagnostic systems are necessarily limited because of their dependence on such speed-sensing devices.
It is an object of the present invention to overcome these, and other limitations of the prior art. Other objects of the present invention will be apparent to those of ordinary skill in the art having the benefit of this disclosure.